A new robotic training method targeting posture and crouch gait in children with cerebral palsy (CP) was developed by a research team from the School of Engineering and Applied Science at Columbia University.
In a pilot study titled “Robot-driven downward pelvic pull to improve crouch gait in children with cerebral palsy,” published in the journal Science Robotics, team leader Sunil Agrawal described how his team’s robotic training system was engineered to improve muscle strength and coordination.
“One of the major reasons for crouch gait is weakness in soleus muscles,” Agrawal, a professor of mechanical engineering and of rehabilitation and regenerative medicine, said in a news release. The soleus is an extensor muscle from just below the knee to the heel that plays a key role in preventing the knee from collapsing and providing propulsion during movement, or gait cycles.
“We hypothesized that walking with a downward pelvic pull would strengthen extensor muscles, especially the soleus, against the applied downward pull and would improve muscle coordination during walking,” Agrawal said.
“We took an approach opposite to conventional therapy with these children: Instead of partial body weight suspension during treadmill walking, we trained participants to walk with a force augmentation,” he said.
Knowing that the soleus muscle is activated more intensely when weight is added to the body during walking, researchers focused on strengthening the soleus, hypothesizing that this would help children with crouch gait increase their standing and walking abilities.
The researchers developed the Tethered Pelvic Assist Device (TPAD) system as a light, wearable, cable-driven robot that assists movement when walking on a treadmill.
“TPAD is a unique device because it applies external forces on the human body during walking,” said Jiyeon Kang, a PhD candidate and lead author of the study. “The training with this device is distinctive because it does not add mass/inertia to the human body during walking.”
Working with six children with cerebral palsy over six weeks, the team examined their muscle strength and coordination while continuously monitoring motion and ground reaction forces.
They found that the training was effective in both enhancing the children’s upright posture and improving their muscle coordination. Other walking features like step length and range of motion also improved.
“Feedback from the parents and children involved in this study was consistent. They reported improved posture, stronger legs, and faster walking speed, and our measurements bear that out,” said Heakyung Kim, a Columbia University professor of pediatrics who treated the children involved in the trial.
“We think that our robotic TPAD training with downward pelvic pull could be a very promising intervention for these children,” Kim added.
Among other symptoms of cerebral palsy, such as slow walking speed or reduced range of motion of the joints, crouch gait is characterized by excessive flexion of the hips, knees, and ankles. It’s caused by a combination of weak extensor muscles that can’t hold an upright posture along with tight flexor muscles that limit the joints’ range of motion.
While providing propulsion to complete the gait cycle, the soleus keeps the shank upright during the mid-stance phase of the cycle to help the knee extend properly.
“Currently, there is no well-established physical therapy or strengthening exercise for the treatment of crouch gait,” Agrawal said.
The research team plans to continue testing the robotic training method in clinical studies, eventually with larger groups of patients and potentially with children who have hemiplegic and quadriplegic cerebral palsy.
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